put those prinfs right in libraries/progress_win.c -> L_OpenProgressWindow() , right before L_IPC_Launch():

	KPrintF("PROGRESS_WIN.c: PW_Screen = %p\n",prog->pw_Screen);
	KPrintF("PROGRESS_WIN.c: PW_Window = %p\n",prog->pw_OwnerWindow);

	KPrintF("PROGRESS_WIN.c: prog->pw_Title = %s\n",prog->pw_Title);
	KPrintF("PROGRESS_WIN.c: prog->pw_Information = %p\n",prog->pw_Information);
	KPrintF("PROGRESS_WIN.c: prog->pw_Information2 = %p\n",prog->pw_Information2);
	KPrintF("PROGRESS_WIN.c: prog->pw_Information3 = %p\n",prog->pw_Information3);

	KPrintF("PROGRESS_WIN.c: prog->pw_SigTask = %p\n",prog->pw_SigTask);
	KPrintF("PROGRESS_WIN.c: prog->pw_SigBit = %p\n",prog->pw_SigBit);
	KPrintF("PROGRESS_WIN.c: prog->pw_Flags = %p\n",prog->pw_Flags);

	KPrintF("PROGRESS_WIN.c: prog->pw_FileCount = %d\n",prog->pw_FileCount);
	KPrintF("PROGRESS_WIN.c: prog->pw_FileSize = %d\n",prog->pw_FileSize);
	
	KPrintF("PROGRESS_WIN.c: prog->pw_FileName = %s\n",prog->pw_FileName);
	
	KPrintF("PROGRESS_WIN.c: prog->pw_TaskName = %s\n",prog->pw_TaskName);

And results:

os3:

PROGRESS_WIN.c: tags = 0x65557f4c
PROGRESS_WIN.c: lib = 0x657124d0
PROGRESS_WIN.c: tag1: 0x80000002, data1: 0x657E2060
PROGRESS_WIN.c: PW_Screen = 0x00000000
PROGRESS_WIN.c: PW_Window = 0x00000000
PROGRESS_WIN.c: prog->pw_Title = Directory Opus
PROGRESS_WIN.c: prog->pw_Information = 0x64be16bc
PROGRESS_WIN.c: prog->pw_Information2 = 0x64be1770
PROGRESS_WIN.c: prog->pw_Information3 = 0x64be17c0
PROGRESS_WIN.c: prog->pw_SigTask = 0x00000000
PROGRESS_WIN.c: prog->pw_SigBit = 0x00000000
PROGRESS_WIN.c: prog->pw_Flags = 0x00000209
PROGRESS_WIN.c: prog->pw_FileCount = 0
PROGRESS_WIN.c: prog->pw_FileSize = 0
PROGRESS_WIN.c: prog->pw_FileName = Opus 5 loading... please wait.
PROGRESS_WIN.c: prog->pw_TaskName = dopus_progressbar



os4:

PROGRESS_WIN.c: tags = 0x654b8f4c
PROGRESS_WIN.c: lib = 0x6ffb8000
PROGRESS_WIN.c: tag1: 0x80000002, data1: 0x680fe060
PROGRESS_WIN.c: PW_Screen = 0x0
PROGRESS_WIN.c: PW_Window = 0x0
PROGRESS_WIN.c: prog->pw_Title = Directory Opus
PROGRESS_WIN.c: prog->pw_Information = 0x650246bc
PROGRESS_WIN.c: prog->pw_Information2 = 0x65024770
PROGRESS_WIN.c: prog->pw_Information3 = 0x650247c0
PROGRESS_WIN.c: prog->pw_SigTask = 0x0
PROGRESS_WIN.c: prog->pw_SigBit = 0x0
PROGRESS_WIN.c: prog->pw_Flags = 0x209
PROGRESS_WIN.c: prog->pw_FileCount = 15
PROGRESS_WIN.c: prog->pw_FileSize = 15
PROGRESS_WIN.c: prog->pw_FileName = Opus 5 loading... please wait.
PROGRESS_WIN.c: prog->pw_TaskName = dopus_progressbar